The technical field of this invention is the topical application of personal care agents and, in particular, soap compositions containing personal care agents.
True soaps are typically formed by the alkaline hydrolysis of fatty esters or fatty acids in a process known as saponification. The resulting alkali metal salts are characterized by a long, oil-soluble, hydrocarbon chain attached to a water-soluble, carboxylate ion, and are particularly useful as wetting agents, emulsifying agents, and as detergents in personal care products. The term soap as used herein includes as well synthetic detergents in which the oil-soluble hydrocarbon chain is attached to a sulfate or sulfonate ion rather than to a carboxylate ion.
The ability to mix beneficial additives, such as fragrances, moisturizers and other therapeutic or desirable agents, is often limited by the tendency of such additives to degrade the physical structure of the soap. For example, fragrance and moisturizer loading for hand soaps and other shaped or compacted soap articles is typically limited to about 3 or 4 percent. At loadings above such levels, the firmness and cohesion of the soap drops off markedly.
There exists a need for better soap compositions, particularly soaps which can incorporate high loadings of liquid personal care agents.